DE69826510T2 - METHOD OF DRILLING AND CEMENTING THROUGH FLAT WATERS - Google Patents

Description

The The present invention relates generally to a composition of materials and a method for applying such Composition during a drilling and cementing process, and in particular relates on a mud system and a method for applying the same mud system for the Promote drilling a well through shallow waters and not stable, not consolidated formations, and the cementing of casings through such an unstable area of a wellbore.

BACKGROUND

since For many years, petroleum companies are focusing on development of oil and gas fields on the mainland. The worldwide demand for energy sources along with falling yields Drilling on the mainland is increasingly leading petroleum companies to Develop offshore reserves.

geological Underwater sediments and structures are often very similar and in some cases geological conditions, which are on the mainland as special productive, far superior. In fact, will be Offshore reserves currently estimated at 21% of the proven reserves of the world, with allegedly 40% to 50% of all future Resources should come from offshore reserves.

The Drilling offshore wells in deep waters with more than about 600 feet depth brings with it its own set of problems. If near one Boundary of a continental shelf will be about 1000 up to 2000 feet below the sludge boundary is often hydrous under geological pressure sandbanks also known as 'Shallow Water Flows' (SWF) are. The depth of these sandbars and the pressures they have create problems for the downhole personnel.

One this problem encountered by the downhole personnel is the type of sand which is associated with the SWFs. This sand seems to exist mainly made of quartz. It is assumed that the grains of sand are rounded and well sorted, and about an average grain diameter of 100 microns or more feature. These grains of sand are loosely packed and unconsolidated, and are like the sand, which on beaches and found in river sand banks will, and promote therefore the instability the formation.

The greatest Challenge to operators of offshore drilling probably from controlling the formation pressure during the entire drilling and Cementing. Drilling muds are usually weighed, to increase the density of the drilling mud and in this way the River of Restrain water from the formation into the borehole. In However, SWF ranges are only a very limited range of drilling mud densities for the Control of the formation pressure of the borehole suitable.

If the drilling mud is too light, water will flow into the well, and this can result in a washout of the wellbore. At first Borehole personnel was still of the opinion that a small flow of water into the Borehole could be used to to reduce the pressure on the aquifer. However, experiments have proved that it is difficult is over control to maintain the borehole when water is flowing into a borehole begins, and that a borehole is normally washed out in this way becomes and gets lost.

on the other hand For example, the pressure within the wellbore may be the column pressure in the Passing sand, though the drilling mud is too heavy, and therefore to splitting the formation to lead. Once a column exists, this column will become usually expand, and can be within a template even to the next one Expand borehole. In addition, you can these columns at low circulation pressures during subsequent drilling be reopened before piping the formation. When columns More and more drilling mud is being formed and spread lost to the formation and causes a massive loss of the circulating drilling mud.

If the annulus of the wellbore is not filled with drilling mud at all times, the hydrostatic pressure within the wellbore may drop until the drilling mud, which has previously been removed by means of the hydrostatic head controlled pressure of the drilling mud, can flow into the borehole. The end result may then consist of a kick or breakout, or a previously stable formation may collapse into the wellbore. Such collapse of the wellbore will result in severe washout and enlargement of the wellbore to an extent where it is no longer possible to continue the drilling process.

Moreover becomes the weight of the mud column that circulates to the earth's surface is added to the hydrostatic pressure column of the wellbore and limits the weight, and ultimately the composition of the applied Drilling mud when the drilling mud circulates to the drilling rig on the earth's surface becomes. For this reason, two methods have been developed for drilling offshore wells Service. These two methods are drilling free and drilling called drilling with a standpipe.

One Standpipe is one piece a piping, which the underwater well with the oil rig connects and makes it possible Drilling mud to the earth's surface to circulate. While stand-alone drilling becomes drilling mud for a single pass applied through the borehole and then directly to the seabed emptied. When drilled in SWF areas without a standpipe, Drilling mud weights of about 11 to 12 lb / gall are required. The desired Drilling mud weight hangs from the environment of the borehole including the water depth and the Depth of the SWF below the mudline.

The Controlling the density of the drilling mud during standpipe-free drilling is a bit more difficult because the drilling mud transports cuts and Solids, and it is therefore not possible to determine how many the same at a certain time in the drilling mud are located. In addition, standpipe-free drilling requires large volumes of drilling mud. Often, standpipe-free drilling requires more mud, as can be stored on a rig, and subjects that Drilling so breaks due to bad weather and the interruption of the supply of drilling mud with boats. The direct emptying of large volumes of cut pieces and Drilling mud on the seabed often raises environmental issues. For the standpipe-free drilling, the staff uses simple mud: this happens both for cost reasons as well as for environmental reasons. Mixed metal silicate sludge and calcium chloride brines are examples of mud, which for standpipe-free SWF drilling is suitable.

The Drilling with a standpipe allows a bigger one flexibility in the selection of the optimal drilling mud components. The additional hydrostatic pressure generated by the mud column is going to the earth's surface ascending, raises the following critical question: "How can to get one completely Formulate working mud, and yet under the Drum weights remain which columns propagate? "Drilling mud weights for the SWF drilling with a standpipe should be within one range of about 8.5 to about 10 lb / gall. Again, it depends the desired drilling mud weight again from the water depth and SWF depth under the seabed from. Still today it is still very difficult and sometimes even impossible a complete one to formulate working mud and at the same time one Make drilling mud with the required light weight.

SUMMARY THE INVENTION

The The invention contemplates a mud system and method of use same liquid of the present invention for stabilizing the formation by placing a unique one Composition of materials in the field of instability, for restraining and Preventing the flow of water into the borehole and restricting one Formation column increase, and for a simpler to perform of drilling and cementing processes.

A embodiment The present invention provides a method for drilling a wellbore through shallow waters, in which a composition is used as drilling mud, which is a fiber material with a large surface area includes; a silicate material; a graphite material; a lightweight Material in the form of hollow microspheres; and a cement material, which can be activated if the same as part of a filter cake is positioned, and thus hardens and the connection of the Promotes filter cake with the cement, which is then introduced into the well, the weight the composition is adapted so that it does not exceed the formation gap gradient.

The Component of the composition work together to form the filter cake to consolidate and loss of fluids from the borehole to prevent.

A another embodiment The present invention provides a method for drilling and cementing a well through shallow waters, wherein the aforesaid method comprises the following:

• (a) drilling and cementing an upper one Section of a borehole, wherein the same upper section is above a Formation in a shallow body of water is;
• (b) drilling through the shallow water formation with Help a lot of drilling mud composition, which is about 8.5 lb / gall until about 10 lb / g, the same composition being a light weight Material in the form of hollow microspheres; and
• (c) cementing the wellbore through the shallow waters with the help of a lightweight cement.

The The invention further provides a drilling mud composition which comprises a fiber material with a large surface area; a silicate material; a graphite material, a lightweight material in the mold hollow microspheres, and a cementitious material which can be activated when the same as Part of a filter cake is positioned, and in this way cures and promotes the association of the filter cake with the cement, which then introduced into the well with the weight of the composition being adapted so that the same does not exceed the formation gap gradient.

The The invention includes a drilling mud for drilling by SWFs, which Silicate, blast furnace slag, cellulose microfibers, hollow microspheres, and Includes graphite particles.

Further Features and Benefits of the drilling mud system for drilling and cementing by SWFs will now be described in greater detail become. A person skilled in the art will immediately recognize that the concept and the specific embodiment described herein very easily as a base for modifying or designing other methods or compositions for the same purpose as that of the present invention can. The skilled person will be further aware of the fact that such equivalent constructions are not of the spirit and scope of the present invention, which in the accompanying claims listed becomes.

DETAILED DESCRIPTION OF THE INVENTION

The The present invention provides a composition of materials and a method for the use of such a composition for drilling a wellbore by SWFs and unstable, unconsolidated formations, and for the Cementing a casing through unstable portions thereof Wellbore.

Since Petroleum companies focus on developing offshore oil and gas reserves they have encountered a number of problems. For example, a whole series of offshore wells are due of shallow waters (SWF) lost.

One Drilling mud consists of a liquid which during a rotary drilling process is circulated through the wellbore. In addition to whose function of chipping chunks to the surface cools and the drilling mud also lubricates the drill bit and drill string and protects against Outbreaks, by holding back the background pressure. He also positions a filter cake on the wall of the borehole, thereby preventing a loss of fluids into the formation. Drilling muds are formulated so that they maintain the hydrostatic pressure within the wellbore can receive which for Preventing a water influence in the borehole is required.

SWF areas represent a challenge to the design of suitable drilling muds because there is only a very narrow pressure window between maintaining the required hydrostatic drilling block pressure and creating crevices within the formation. The appropriate mud weight will depend on a number of variables that include water depth and depth below the seabed in the area where the SWFs and unconsolidated sand were found. Drilling muds are formulated to meet the requirements of each well site. The present invention includes a number of components or elements which together work to control SWFs.

in the general includes an embodiment the present invention, a suspension medium, lost circulating materials, lightweight materials, and filter cake reinforcement materials.

drilling fluids should be a suitable suspending medium for suspending the solids which are added to the drilling mud as lost circulating materials, and for suspending the drill bit cuts within the drilling mud, if the same to the earth's surface is circulated up. Materials for adjusting the carrying capacity and the suspension capacity of the drilling mud, close Hyrdoxyethylcellulose, Welangum, guar gum, xanthan gum, polyacrylamide / polyacrylate, or carboxymethylcellulose but are not limited to these.

drill operator often encounters zones which, due to cracks, coarse sand, Gravel, or other formations large volumes of drilling mud record. To control such a heavy loss of drilling mud the staff circulates sufficiently large solids, which in be suspended in the drilling mud. These solid particles will be used to bridge particularly permeable formations and To seal, to promote the sifting of tips, and an enlargement of Prevent columns. Such solids are called lost circulating materials designated.

A preferred embodiment The present invention uses fibrous materials having a large size surface area for the Tying the unconsolidated sand and promoting the deposition of a robust Filter cake on the surface of the borehole. Cellulose microfibers are preferred, though also other fibers with similar ones Characteristics, such as glass microfibers can. Promote cellulose microfibers In addition, the viscose of the drilling mud and increase the carrying and suspension capacity of drilling mud.

suitable Drilling mud for the application in SWFs can also deformable graphite particles and / or a hydratable Include sound. Graphite particles and clay can be combined with cellulosic fibers with large surface areas for sealing especially permeable Formations and promoting the screening of column tips are applied. In this way can the graphite particles and the clay in the closing of columns and helping to prevent the loss of circulating fluid. Preferred embodiments of the present invention include one or more of these materials. The product STEEL SEAL of the company Superior Graphite represents a preferred deformable Graphite material for The addition to a drilling mud, and represents prehydrogenated bentonite a preferred tone for these mud systems.

As already mentioned above It is particularly difficult to get a drilling mud of the proper density for the Drilling through SWFs weighing about 8.5 to about 10 lb / gall to formulate. Completely working drilling mud for standpipe-free drilling by SWFs usually weighs in between approximately 10 lb / gall and 12 lb / gall, though such weight during one Drilling with a standpipe would often produce gaps. The Density of the drilling mud must therefore with the help of lightweight Controlled materials such as hollow glass, ceramic or microspheres become.

SWFs have gap gradients, which barely exceed its pore pressure. Successful drilling through SWFs therefore depends on the ability a sufficiently large weight for stabilizing the borehole to be able to produce without exceeding the formation gap gradient. Because the hollow microspheres are lighter than water can the same to be applied, concentrated mud to formulate chemical components with weights containing the Do not exceed formation gap gradient. A preferred embodiment The present invention uses hollow glass microspheres a specific gravity of about 0.125 to about 0.6, to increase in this way the volume of the drilling mud, without To give too much weight to the same drilling mud. The caves microspheres can also be applied to the weight of cementing compositions to control which during applied to the casing of unstable areas of the wellbore become.

preferred embodiments The drilling mud system also includes an activatable, fast curing Cement material. There may be quite a lot of cement materials for this Drilling mud can be applied. Close examples of such materials Portland cement, fly ash, blast furnace slag (BFS), and mixtures the same one. Preferred embodiments of the drilling mud system include BFS in the drilling mud.

The Including BFS in the drilling mud supports the other component of drilling mud during the combination of unconsolidated sand and the closure of columns. In addition, such inclusion of BFS increases into the drilling mud and its inclusion in the filter cake on the surface the borehole compatibility of filter cake with cement. The FSO inside the filter cake Therefore, the formation of a strong connection between the filter cake and promote the cement, if the operating personnel with the cementing of the piping starts.

One The advantage of the BFS is the fact that it is made of a latent hydraulic Cement material that does not react easily with water, and which if desired can be activated in a high pH environment. BFS indurated in a high pH environment (greater than or equal to pH) from 13 accordingly). The pH of the drilling mud can therefore increase maintain a pH which is lower than the pH, which for activating the curing process of BFS is required. By controlling the activation of the BFS allows the operating staff to position the BFS in the filter cake enable, before it hardens. After positioning, the filter cake with a rinse with purged to a high pH which are generally made from a mixture of sodium hydroxide and sodium carbonate persists and over has a pH of pH14. The conditioner hardened with the high pH the FSO and supported the connection of the cement with the filter cake.

desirable Properties for Drilling mud for control of BWFs preclude the use of lightweight Solids which provide a robust, resistant filter cake and produce a filtrate which is in unconsolidated sand stabilizing gel will produce. The drilling mud system of present invention uses admixtures of materials which work together to the fundamental already described above To achieve goals.

Some examples of drilling mud systems incorporating the additives listed above include silicate systems, mixed metal silicate systems, and partially hydrolyzed polyacrylamide (PHPA) systems. Silicate systems are preferred because they form gels and gelatinous settlements when in contact with cations such as Ca ⁺⁺ , Mg ⁺⁺ or H ⁺ within the wellbore. Silicates, which are lost to the formation when the filtrate contacts these cations, form gels in situ and strengthen unconsolidated formations near the wellbore. In addition, the infusion of a silicate into the drilling mud will promote the bonding of the cement to the filter cake formed on the sides of the wellbore.

Examples of drilling mud compositions suitable for drilling by SWFs are both like the properties of such compositions listed in Tables 1 to 3. The testing of the drilling mud compositions was in accordance with the regulations from API RP 13B. additionally for the fluid loss tests described in RP 13B from filter paper were also fluid loss tests with the help of ceramic discs with an average Pore diameter of 35 microns performed. Tests with discs with a bigger one Pore diameters were carried out because the unconsolidated sand present in SWFs seems to have one having large pore diameter.

Tabelle 2 Charakteristiken der in Tabelle 1 aufgeführten Bohrschlamme

Tabelle 3 Identifizierung und Funktion von Flüssigkeitsbestandteilen

The examples below are illustrative only, and applications are not limited thereto. Table 1 Drilling mud for shallow waters

Table 2 Characteristics of the drilling muds listed in Table 1

Table 3 Identification and Function of Liquid Components

The listed above Examples are representative for suitable Drilling mud for drilling through SWFs. Numerous modifications and variations the drilling mud composition are in consideration of the above instructions possible. It becomes clear that the invention is within the scope the accompanying claims also differently than here specifically described can be used The application of the drilling mud system described above during the Drilling through and cementing formations into SWFs described below. The first stage of this drilling / cementing process consists of drilling a hole down to the top of the hole Section of the formation, which is the unstable sand or other unconsolidated materials, and the tubing of the Borehole at this time.

The Drilling will then be using the drilling mud system of the present Invention continued. In a preferred embodiment become the cellulosic microfibers with the BFS, graphite particles, and formation sand (which is released by drilling), a robust, impermeable To form filter cake or a mat. Together with the respective ones Polymern and maybe a silica gel stabilizes this mat the free-flowing sand, which is characteristic of SWFs. Cellulose microfibers also work together with deformable Graphite particles and clay to seal particularly permeable formations and restrict column propagation.

If the borehole down to the desired one Depth has been drilled, the piping is determined by the SWF and with the help of an activated, fast-curing cement material such as For example, BFS is cemented in this position. A preferred embodiment This cementing process uses a foamed cement or a cement containing hollow glass microspheres for density control.

One Borehole failure may occur during the cementing process or even occur later when the cement piping not well connected to the filter cake. If BFS or a other activatable cementitious material is applied in the drilling mud and was included in the filter cake, the cement material activated and cured be, and will promote the connection of the filter cake with the cement. One Advantage of BFS is the fact that their activation with a low pH during the entire drilling process delayed, and then just before cementing very easy with help a rinse can be activated with a high pH.

In Considering the instructions described above, there are many modifications and variations of the mud system and application of the same mud system for the Drilling and cementing by SWFs conceivable. A specialist This area will therefore immediately recognize that a whole series of different embodiments can be applied without departing from the principles of the appended claims.

Claims (15)

A method for drilling a borehole through shallow waters, in which a composition is used as drilling mud, which is a fiber material with a large surface area, a Silicate material, a graphite material, a lightweight material in the form of hollow microspheres, and includes a cementitious material which after positioning as part of a filter cake can be activated to the same to harden and to promote bonding of the filter cake to a cement which is subsequently introduced into the wellbore, wherein the weight The composition is adapted to the formation gap gradient does not exceed. A method according to claim 1, wherein the fibrous material Made of cellulosic microfibers. A method according to claim 1 or 2, wherein the composition includes a lightweight material which again hollow microspheres with a lower density than water, and preferably hollow glass microspheres with gravity of about 0.125 to about 0.6. A method according to claim 1, 2 or 3, wherein The cement material can be activated so that the same indurated and its pH changed. A method according to claim 1, 2, 3, or 4, wherein the cement material includes blast furnace slag. A method according to any of the above claims 1 to 5, in which the graphite material of deformable graphite particles consists. A method according to any of the above claims 1 to 6, in which the composition includes a clay material, which preferably consists of prehydrated bentonite. A method according to claim 7, wherein the fiber material, the graphite material, and the clay particles control the loss of liquid from the borehole. A method according to any of the above claims 1 to 8, in which the weight of the composition is about 8.5 lb / gall until about 10 lb / gall. A method according to any of the above claims 1 to 9, in which the silicate, the microfibers, the graphite particles, the clay and cement materials are enclosed in the filter cake become. A method according to any of the above claims 1 to 9, in which the silicate, the microfibers, the graphite particles, the clay and cement material reinforcing poorly consolidated Support formations. A procedure for the drilling and cementing of a well in shallow waters, wherein the same method comprises the following: (a) drilling and Cementing an upper portion of a well, the same upper section over a formation lies in shallow waters; (b) drilling by the formation in the aforementioned shallow waters with Helping a lot of drilling mud composition, which is about 8.5 lb / gall until about 10 lb / g, the same composition being a light weight Material in the form of hollow microspheres; and (c) the Cementing the wellbore through the shallow waters with the help of a lightweight cement. A method according to claim 12, wherein the Composition of one of those which in claims 1 to 9 are defined. A drilling mud composition which is a fiber material with a large surface area, a silicate material, a graphite material, a lightweight Material in the form of hollow microspheres, and a cement material which can be activated if the same as part a filter cake is positioned to harden and promoting the bonding of the filter cake to the cement, which is subsequently introduced into the wellbore, wherein the weight the composition is adapted to the formation gap gradient does not exceed. A drilling mud composition according to claim 14, which corresponds to the definition of one of the above claims 2 to 9.